203 research outputs found
Special Issue on Emergent Effects in Stochastic Neural Networks with Application to Learning and Information Processing
Special Issue on Emergent Effects in Stochastic Neural Networks with Application to Learning and Information Processing
Decoupling of defect and short-range order contributions to resistivity recovery measurements in binary alloys
© 2014 American Physical Society. We report a new and improved approach that uses low-temperature resistivity recovery measurements to study the defect kinetics in metallic binary alloys. This method is able to decouple the effect related to the irradiation defect contribution to the resistivity from that of the short-range order, which is enhanced by the free migration of defects. This approach can provide reliable experimental data which are more suitable for comparisons with current computational models. Furthermore, the difference in this method with respect to the classical one is that our method gives information concerning the role of vacancies and interstitials on short-range order. The method is applied to a model alloy Fe-5%Cr, of interest for fusion applications, where short-range order effects have been previously found to play a role.Peer Reviewe
New model to explain the EQ-5D VAS in patients who have undergone spinal fusion
Background: In the health sector, the EQ-5D has been widely used to evaluate health-related quality of life, mainly due to its simplicity, robustness and plasticity in calculating years of life adjusted for quality. Methods: However, its model has remained stable over time and knowledge of the influence of such biodemographical variables as age and gender has not been incorporated. This information, along with the well-known non-linear behavior of the VAS, which measures the self-concept of the 'General State of Health', forms the basis for a new model, which we present here from a sample of patients who were operated on for chronic low back pain. Results: These are obtained using multiple regression analysis are consistent in terms of goodness-of-fit given that this new model is able to explain 91.3% of the self-concept of the 'general state of health'. Conclusions: Above leads to an improvement of 21.6% compared to the available models more robust and meets most of the restrictions for this type of statistical modeling
Superelastic damping at nanoscale in ternary and quaternary Cu-based shape memory alloys
Superelasticity is a characteristic thermomechanical property in shape memory alloys (SMA), which is due to a reversible stress-induced martensitic transformation. Nano-compression experiments made possible the study of this property in Cu–Al–Ni SMA micropillars, showing an outstanding ultra-high mechanical damping capacity reproducible for thousands of cycles and reliable over the years. This scenario motivated the present work, where a comparative study of the damping capacity on four copper-based SMA: Cu–Al–Ni, Cu–Al–Be, Cu–Al–Ni–Be and Cu–Al–Ni–Ga is approached. For this purpose, [001] oriented single-crystal micropillars of comparable dimensions (around 1 µm in diameter) were milled by focused ion beam technique. All micropillars were cycled up to two hundred superelastic cycles, exhibiting a remarkable reproducibility. The damping capacity was evaluated through the dimensionless loss factor η, calculated for each superelastic cycle, representing the dissipated energy per cycle and unit of volume. The calculated loss factor was averaged between three micro-pillars of each alloy, obtaining the following results: Cu–Al–Ni η = 0.20 ± 0.01; Cu–Al–Be η = 0.100 ± 0.006; Cu–Al–Ni–Be η = 0.072 ± 0.004 and Cu–Al–Ni–Ga η = 0.042 ± 0.002. These four alloys exhibit an intrinsic superelastic damping capacity and offer a wide loss factor band, which constitutes a reference for engineering, since this kind of micro/nano structures can potentially be integrated not only as sensors and actuators but also as dampers in the design of MEMS to improve their reliability. In addition, the study of the dependence of the superelastic loss factor on the diameter of the pillar was approached in the Cu–Al–Ni–Ga alloy, and here we demonstrate that there is a size effect on damping at the nanoscale.Fil: Gómez Cortés, J.F.. Universidad del País Vasco; EspañaFil: Fuster, Valeria de Los Angeles. Universidad del País Vasco; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Pérez Cerrato, M.. Universidad del País Vasco; EspañaFil: Lorenzo, P.. Universidad del País Vasco; EspañaFil: Ruiz Larrea, I.. Universidad del País Vasco; EspañaFil: Breczewski, T.. Universidad del País Vasco; EspañaFil: Nó, M. L.. Universidad del País Vasco; EspañaFil: San Juan, J. M.. Universidad del País Vasco; Españ
Insights onto the magnetic coupling at hexaferrite-based hard/soft bilayer systems
IBERTRIVA 2019 X Iberian Conference on Tribology – IBERTRIB, XI Iberian Vacuum Conference - RIVA, Seville, Spain,June 26-28Magnets are used in a variety of applications, such as generators, magnetic recording media,
components in RF and microwave devices. However, many of these magnets contain s rare
earths, critical elements whose extraction is environmentally harmful and that present price
volatility risks. Their replacement by cheaper and more environmentally friendly materials is
therefore sought.
In our case, we have focused on magnetically hard strontium hexaferrite (SrFe 12O19, SFO) as
the base for alternative permanent magnets (Figure 1a). The atomic arrangement of this ferrite
results in a high magnetocrystalline anisotropy and a coercive field, however, its magnetization
is moderate (1). It is well known that the coupling between a magnetically hard and soft material
improved magnetization while avoiding a high cost in coercitivity loss (2). However, results have
been disappointing so far as structural and geometrical limitations make it extremely challenging
to fabricate. In this work, we aim at further understanding the magnetic coupling at hard -soft
interfaces involving ferrites, for which we have deposited soft iron and cobalt metals on top of
SrFe12O19 thin films with controlled easy-axis of magnetization.
SFO thin films have been obtained by RF magnetron sputtering at 260W followed by a
subsequent annealing in air of 850ºC. Their structure and composition was characterized by
Raman spectroscospy (Figure 1b), Mössbauer spectroscopy, X-ray photoemission
spectroscopy and low-energy electron microscopy (LEEM). We have grown the magnetically
soft layer by molecular-beam epitaxy and we have analyzed the resulting bilayer system
through photoemission electron microscopy, LEEM and vibrating-sample magnetometry.
References
[1] R.C. Pullar, Hexagonal ferrites: a review of the synthesis, properties and applications of hexaferrite ceramics, Progress in Materials Science 57 (2012), pp 1191¿1334.
[2] Eric E. Fullerton, J. S. Jiang, M. Grimsditch, C. H. Sowers, and S. D. Bader, Exchange-spring behavior in epitaxial hard/soft magnetic bilayers, Phys. Rev. B 58 (1998) 1219
Designing for shape memory in additive manufacturing of Cu-Al-Ni shape memory alloy processed by laser powder bed fusion
Shape memory alloys (SMAs) are functional materials that are being applied in practically all industries, from aerospace to biomedical sectors, and at present the scientific and technologic communities are looking to gain the advantages offered by the new processing technologies of additive manufacturing (AM). However, the use of AM to produce functional materials, like SMAs, constitutes a real challenge due to the particularly well controlled microstructure required to exhibit the functional property of shape memory. In the present work, the design of the complete AM processing route, from powder atomization to laser powder bed fusion for AM and hot isostatic pressing (HIP), is approached for Cu-Al-Ni SMAs. The microstructure of the different processing states is characterized in relationship with the processing parameters. The thermal martensitic transformation, responsible for the functional properties, is analyzed in a comparative way for each one of the different processed samples. The present results demonstrate that a final post-processing thermal treatment to control the microstructure is crucial to obtain the expected functional properties. Finally, it is demonstrated that using the designed processing route of laser powder bed fusion followed by a post-processing HIP and a final specific thermal treatment, a satisfactory shape memory behavior can be obtained in Cu-Al-Ni SMAs, paving the road for further applications
Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
We review HB stars in a broad astrophysical context, including both variable
and non-variable stars. A reassessment of the Oosterhoff dichotomy is
presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of
globular clusters (GCs) in the HB morphology-metallicity plane both exclude,
with high statistical significance, the possibility that the Galactic halo may
have formed from the accretion of dwarf galaxies resembling present-day Milky
Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the
second-parameter problem is presented. A technique is proposed to estimate the
HB types of extragalactic GCs on the basis of integrated far-UV photometry. The
relationship between the absolute V magnitude of the HB at the RR Lyrae level
and metallicity, as obtained on the basis of trigonometric parallax
measurements for the star RR Lyrae, is also revisited, giving a distance
modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are
studied. Finally, the conductive opacities used in evolutionary calculations of
low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and
Space Scienc
Centrality dependence of charged particle production at large transverse momentum in Pb-Pb collisions at TeV
The inclusive transverse momentum () distributions of primary
charged particles are measured in the pseudo-rapidity range as a
function of event centrality in Pb-Pb collisions at
TeV with ALICE at the LHC. The data are presented in the range
GeV/ for nine centrality intervals from 70-80% to 0-5%.
The Pb-Pb spectra are presented in terms of the nuclear modification factor
using a pp reference spectrum measured at the same collision
energy. We observe that the suppression of high- particles strongly
depends on event centrality. In central collisions (0-5%) the yield is most
suppressed with at -7 GeV/. Above
GeV/, there is a significant rise in the nuclear modification
factor, which reaches for GeV/. In
peripheral collisions (70-80%), the suppression is weaker with almost independently of . The measured nuclear
modification factors are compared to other measurements and model calculations.Comment: 17 pages, 4 captioned figures, 2 tables, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/284
Measurement of charm production at central rapidity in proton-proton collisions at TeV
The -differential production cross sections of the prompt (B
feed-down subtracted) charmed mesons D, D, and D in the rapidity
range , and for transverse momentum GeV/, were
measured in proton-proton collisions at TeV with the ALICE
detector at the Large Hadron Collider. The analysis exploited the hadronic
decays DK, DK, DD, and their charge conjugates, and was performed on a
nb event sample collected in 2011 with a
minimum-bias trigger. The total charm production cross section at TeV and at 7 TeV was evaluated by extrapolating to the full phase space
the -differential production cross sections at TeV
and our previous measurements at TeV. The results were compared
to existing measurements and to perturbative-QCD calculations. The fraction of
cdbar D mesons produced in a vector state was also determined.Comment: 20 pages, 5 captioned figures, 4 tables, authors from page 15,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/307
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